Communication system and method using space division multi-user multiple input multiple output (SD-MIMO) communication method

ABSTRACT

Provided is a communication system using a space division multi-user multiple input multiple output (SD-MIMO) communication method. A transmission apparatus may transmit, to each of terminals included within a coverage, common control information commonly transmitted to the terminals and individual control information individually transmitted to each of the terminals. The transmission apparatus does not precode the common control information and transmits the non-precoded common control information. The transmission apparatus precodes the individual control information and transmits the precoded individual control information.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit under 35 U.S.C. §119(a) of KoreanPatent Application No. 10-2009-0119859, filed on Dec. 4, 2009, in theKorean Intellectual Property Office, the entire disclosure of which isincorporated herein by reference for all purposes.

BACKGROUND

1. Field

The following description relates to a method of transmitting andreceiving data using a wireless network.

2. Description of Related Art

In a space division multi-user multiple input multiple output (SD-MIMO)communication method, precoding may correspond to a process ofappropriately allocating spatial beams to users.

Multiple-input and multiple-output (MIMO) includes three maincategories: precoding, spatial multiplexing or SM, and diversity coding.Beamforming increases the signal gain from constructive interference andreduces the multipath fading effect. When the receiver has multipleantennas, precoding is used to simultaneously maximize the signal levelat the receiving antennas. In spatial multiplexing, a high rate signalis split into multiple lower rate streams, and each stream istransmitted from a different transmit antenna in the same frequencychannel. In diversity coding, a single stream is coded using space-timecoding and transmitted. Spatial multiplexing can also be combined withprecoding or combined with diversity coding.

A transmission apparatus may receive channel status information fromterminals, and may select a terminal to receive data using precodingbased on the received channel status information. The transmissionapparatus may perform precoding based on the channel status information.

A terminal may receive a training signal from the transmissionapparatus, and estimate a channel between the transmission apparatus andthe terminal using the received training signal to generate channelstatus information.

In the SD-MIMO communication method, the transmission apparatus mayemploy a plurality of transmit antennas and thus the channel between thetransmission apparatus and the terminal may be provided in a vector ormatrix form. To estimate the channel in the vector or matrix form, thetransmission apparatus may transmit an individual training signal foreach transmit antenna.

SUMMARY

A transmission apparatus to transmit data to a plurality of terminalscomprising at least one receive antenna, the transmission apparatuscomprising a common control information generator configured to generatecommon control information with respect to the plurality of terminals,an individual control information generator configured to generateindividual control information with respect to each of the terminals, aprecoder configured to generate precoded data with respect to each ofthe terminals by precoding the individual control information and datawith respect to each of the terminals and a transmitter configured totransmit, to the plurality of terminals, a data frame comprising thecommon control information and the precoded data according to amulti-user multiple input multiple output (MU-MIMO) communicationmethod.

The common control information comprises one or more of a precodingmethod applied to the data frame, a number of terminals supported by thedata frame, a number of data streams included in the data frame, aduration or a length of a channel estimation field included in the dataframe, and a format of the channel estimation field.

A power amplifier training signal generator configured to generate apower amplifier training signal for a multi-antenna automatic gaincontrol (AGC) of each of the terminals, wherein the precoder is furtherconfigured to generate the precoded data by additionally precoding thepower amplifier training signal.

The individual control information comprises one or more of a length ofthe data frame, a modulation and coding method applied to the data withrespect to each of the terminals, a channel bandwidth, a channelsmoothing, a channel aggregation, an error correction code, and a lengthof a guard interval.

A channel estimation signal generator configured to generate a channelestimation signal used for a channel estimation of each of theterminals, wherein the precoder is further configured to generate theprecoded data by additionally precoding the channel estimation signal.

In one general aspect, there is provided a transmission apparatus totransmit data to a plurality of terminals including at least one receiveantenna, the transmission apparatus including: a common controlinformation generator configured to generate common control informationwith respect to the plurality of terminals, an individual controlinformation generator configured to generate individual controlinformation with respect to each of the terminals, a precoder configuredto generate precoded data with respect to each of the terminals byprecoding the individual control information and data with respect toeach of the terminals, and a transmitter configured to transmit, to theplurality of terminals, a data frame including the common controlinformation and the precoded data according to a multi-user multipleinput multiple output (MU-MIMO) communication method.

The transmission apparatus may include that the common controlinformation includes one or more of: a precoding method applied to thedata frame, a number of terminals supported by the data frame, a numberof data streams included in the data frame, a duration or a length of achannel estimation field included in the data frame, and a format of thechannel estimation field.

The transmission apparatus may further include including: a poweramplifier training signal generator configured to generate a poweramplifier training signal for a multi-antenna automatic gain control(AGC) of each of the terminals, wherein the precoder is furtherconfigured to generate the precoded data by additionally precoding thepower amplifier training signal.

The transmission apparatus may include that the individual controlinformation includes one or more of: a length of the data frame, amodulation and coding method applied to the data with respect to each ofthe terminals, a bandwidth of a using channel, a channel smoothing, achannel aggregation, an error correction code, and a length of a guardinterval.

The transmission apparatus may further include: a channel estimationsignal generator configured to generate a channel estimation signal usedfor a channel estimation of each of the terminals, wherein the precoderis further configured to generate the precoded data by additionallyprecoding the channel estimation signal.

The transmission apparatus may further include: a controller configuredto: individually determine a number of data streams transmitted to eachof the terminals, and determine a number of channel estimation signalgroups based on the number of data streams, wherein the data frameincludes a plurality of data streams, and wherein the channel estimationsignal includes a plurality of channel estimation signal groups.

The transmission apparatus may include that: the transmitter is furtherconfigured to transmit a plurality of precoded data to a particularterminal included in the plurality of terminals, and each of channelestimation signals included in the plurality of precoded data isincluded in a different time interval.

The transmission apparatus may include that the individual controlinformation is modulated using a predetermined modulation method, or iserror correction coded using a predetermined error correction codemethod.

In another general aspect, there is provided a terminal connected to atransmission apparatus, the terminal including: a receiver configured toreceive a data frame from the transmission apparatus, a common controlinformation decoder configured to decode, from the data frame, commoncontrol information commonly transmitted to the terminal and to a secondterminal that are connected to the transmission apparatus, an individualcontrol information decoder configured to decode, from the data frame,individual control information individually determined with respect toeach of the terminal and the second terminal based on the common controlinformation, and a data decoder configured to decode data, included inthe data frame, based on the individual control information, wherein theindividual control information and the data are precoded and arereceived.

The terminal may include that the common control information includesone or more of: a precoding method applied to the data frame, a numberof terminals supported by the data frame, a number of data streamsincluded in the data frame, a duration or a length of a channelestimation field included in the data frame, and a format of the channelestimation field.

The terminal may include that the individual control informationincludes one or more of: a length of the data frame, a modulation andcoding method applied to the data with respect to each of the terminals,a bandwidth of a using channel, a channel smoothing, a channelaggregation, an error correction code, and a length of a guard interval.

The terminal may include that the individual control information decoderis further configured to decode the individual control information usinga predetermined modulation method or a predetermined error correctioncode method.

The terminal may further include: a channel estimator configured toestimate a channel between the terminal and the transmission apparatusbased on a channel estimation signal, wherein the data frame includesthe channel estimation signal, and wherein the data decoder is furtherconfigured to decode the data based on the estimated channel.

The terminal may include that: the data frame includes a plurality ofdata streams, each of the data streams includes the channel estimationsignal, and the channel estimation signal included in each of the datastreams is included in a different time interval.

The terminal may include that: the data frame includes a plurality ofdata streams, the channel estimation signal includes a plurality ofchannel estimation signal groups, and a number of the channel estimationsignal groups is determined based on a number of the data streams.

The terminal may include that the receiver is further configured toreceive the data frame via at least one receive antenna.

In another general aspect, there is provided a method of transmittingdata to a plurality of terminals including at least one receive antenna,the method including: generating common control information with respectto the plurality of terminals, generating individual control informationwith respect to each of the terminals, generating precoded data withrespect to each of the terminals by precoding the individual controlinformation and data with respect to each of the terminals, andtransmitting, to the plurality of terminals, a data frame including thecommon control information and the precoded data according to a MU-MIMOcommunication method.

The method may include that the common control information includes oneor more of: a precoding method applied to the data frame, a number ofterminals supported by the data frame, a number of data streams includedin the data frame, a duration or a length of a channel estimation fieldincluded in the data frame, and a format of the channel estimationfield.

The method may include that the individual control information includesone or more of: a length of the data frame, a modulation and codingmethod applied to the data with respect to each of the terminals, abandwidth of a using channel, a channel smoothing, a channelaggregation, an error correction code, and a length of a guard interval.

The method may further include: generating a channel estimation signalused for a channel estimation of each of the terminals, wherein theprecoding includes generating the precoded data by additionallyprecoding the channel estimation signal.

In another general aspect, there is provided a method of receiving data,the method including: receiving a data frame from the transmissionapparatus, decoding, from the data frame, common control informationcommonly transmitted to the terminal and to a second terminal that areconnected to the transmission apparatus, decoding, from the data frame,individual control information individually determined with respect toeach of the terminal and the second terminal based on the common controlinformation, and decoding data, included in the data frame, based on theindividual control information, wherein the individual controlinformation and the data are precoded and are received.

The method may further include: estimating a channel between theterminal and the transmission apparatus based on a channel estimationsignal, wherein the data frame includes the channel estimation signal,and the decoding of the data includes decoding the data based on theestimated channel.

The method may include that: the data frame includes a plurality of datastreams, each of the data streams includes the channel estimationsignal, and the channel estimation signal included in each of the datastreams is included in a different time interval.

In another general aspect, there is provided a non-transitorycomputer-readable recording medium storing a program to implement themethod of claim 17.

Other features and aspects will be apparent from the following detaileddescription, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a data transmission using a multi-usermultiple input multiple output (MU-MIMO) communication method accordingto an embodiment.

FIG. 2 is a diagram illustrating a structure of a data frame accordingto an embodiment.

FIG. 3 is a diagram illustrating a structure of a data frame furtherincluding legacy control information to support terminals according toan embodiment.

FIG. 4 is a diagram illustrating a data frame when a particular terminalreceives a plurality of data streams according to an embodiment.

FIG. 5 is a diagram illustrating an example of a data frame in whichdata streams are independently separated and transmitted using precoding

FIG. 6 is a diagram illustrating an example of data streams includingchannel estimation signal groups in different time intervals withrespect to the same terminal according to an embodiment.

FIG. 7 is a diagram illustrating an example of data streams includingchannel estimation signal groups in different time intervals withrespect to different terminals according to an embodiment.

FIG. 8 is a diagram illustrating an example of a data frame in whichdata streams are independently separated and transmitted usingprecoding.

FIG. 9 is a block diagram illustrating a configuration of a transmissionapparatus according to an embodiment.

FIG. 10 is a block diagram illustrating a configuration of a terminalaccording to an embodiment.

FIG. 11 is a flowchart illustrating a method of receiving data accordingto an embodiment.

FIG. 12 is a flowchart illustrating a method of transmitting dataaccording to an embodiment.

Throughout the drawings and the detailed description, unless otherwisedescribed, the same drawing reference numerals will be understood torefer to the same elements, features, and structures. The relative sizeand depiction of these elements may be exaggerated for clarity,illustration, and convenience.

DETAILED DESCRIPTION

The following detailed description is provided to assist the reader ingaining a comprehensive understanding of the methods, apparatuses,and/or systems described herein. Accordingly, various changes,modifications, and equivalents of the systems, apparatuses, and/ormethods described herein will be suggested to those of ordinary skill inthe art. The progression of processing steps and/or operations describedis an example; however, the sequence of and/or operations is not limitedto that set forth herein and may be changed as is known in the art, withthe exception of steps and/or operations necessarily occurring in acertain order. Also, description of well-known functions andconstructions may be omitted for increased clarity and conciseness.

FIG. 1 illustrates a data transmission using a multi-user multiple inputmultiple output (MU-MIMO) communication method according to anembodiment.

Referring to FIG. 1, a transmission apparatus 110 transmits data toterminals 181 and 182 via transmit antennas 151 and 152. A precoder 140of the transmission apparatus 110 may precode data streams 120 and 130using a precoding matrix.

The precoded data streams may be transmitted to the terminals 181 and182 using vector channels 161, 162, 163, and 164. Although theillustrated terminal 181 includes a single receive antenna 171 and theterminal 182 includes a single receive antenna 172 in FIG. 1, each ofthe terminals 181 and 182 may include a plurality of receive antennas.

Each of the terminals 181 and 182 may receive the data streamstransmitted using the vector channels 161, 162, 163, and 164. A signalreceived by the terminal 181 may be expressed by the following Equation1.

$\begin{matrix}{\left\lbrack y_{1} \right\rbrack = \begin{matrix}{{\begin{bmatrix}h_{11} & h_{12}\end{bmatrix} \cdot \begin{bmatrix}t_{11} \\t_{21}\end{bmatrix} \cdot \left\lbrack x_{1} \right\rbrack} + {\begin{bmatrix}h_{11} & h_{12}\end{bmatrix} \cdot}} \\{{\begin{bmatrix}t_{12} \\t_{22}\end{bmatrix} \cdot \left\lbrack x_{2} \right\rbrack} + {\quad\left\lbrack n_{1} \right\rbrack}}\end{matrix}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

A signal received by the terminal 182 may be expressed by the followingEquation 2.

$\begin{matrix}{\left\lbrack y_{2} \right\rbrack = \begin{matrix}{{\begin{bmatrix}h_{21} & h_{22}\end{bmatrix} \cdot \begin{bmatrix}t_{11} \\t_{21}\end{bmatrix} \cdot \left\lbrack x_{1} \right\rbrack} + {\begin{bmatrix}h_{21} & h_{22}\end{bmatrix} \cdot}} \\{{\begin{bmatrix}t_{12} \\t_{22}\end{bmatrix} \cdot \left\lbrack x_{2} \right\rbrack} + {\quad\left\lbrack n_{2} \right\rbrack}}\end{matrix}} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

In one example, x₁ and x₂ denote the data streams to be transmitted fromthe transmission apparatus 110 to the terminals 181 and 182,respectively; y₁ and y₂ denote the signals received by the terminals 181and 182, respectively; and h₁₁, h₁₂, h₂₁, and h₂₂ denote statuses ofradio channels formed between each of the transmit antennas 151 and 152and each of the receive antennas 171 and 172. Also, [t₁₁, t₂₁] denotes aprecoding vector of the terminal 181, [t₁₂, t₂₂] denotes a precodingvector of the terminal 182, and n₁ and n₂ denote thermal noise.

Referring to the above Equation 1, the transmission apparatus 110 maydetermine the precoding vector [t₁₂, t₂₂] such that an inner productvalue of a channel vector [h₁₁ h₁₂] with respect to the terminal 181 andthe precoding vector [t₁₂, t₂₂] with respect to the terminal 182 maybecome a very small value. In one example, interference of the datastream x₂ against the terminal 181 may decrease.

Similarly, referring to the above Equation 2, the transmission apparatusmay determine the precoding vector [t₁₁, t₂₁] such that an inner productvalue of a channel vector [h₂₁ h₂₂] with respect to the terminal 182 andthe precoding vector [t₁₁, t₂₁] with respect to the terminal 181 maybecome a very small value. In one example, interference of the datastream x₁ against the terminal 182 may decrease.

The transmission apparatus 110 may receive channel status informationfrom each of the terminals 181 and 182 to verify the channel statusinformation, and may determine a precoding vector so that a channelvector and the precoding vector may mutually have a small inner productvalue.

When the transmission apparatus 110 transmits, to the terminals 181 and182, a data frame including a first data frame and a second data frame,a length of the second data frame received by the terminal 181 may bevery short. Accordingly, an amount of interference caused by the seconddata stream may be very small and the terminal 181 may decode the firstdata stream. Similarly, the terminal 182 may decode the second datastream.

Each of the terminals 181 and 182 may receive a training signal from thetransmission apparatus 110 to estimate a channel status using thetraining signal. As shown in FIG. 1, when the transmission apparatus 110includes the plurality of transmit antennas 151 and 152, thetransmission apparatus 110 may transmit a specially designed trainingsignal to each of the terminals 181 and 182, such that each of theterminals 181 and 182 may identify the training signal transmitted fromeach of the transmit antennas 151 and 152.

FIG. 2 illustrates a structure of a data frame according to anembodiment. The data frame includes a signal detection field 211, afirst channel estimation field 212, a common control field 213, andprecoded data 220.

Precoding may not be applied to the signal detection field 211, thefirst channel estimation field 212, and the common control field 213.

The precoded data 220 corresponds to information that is precoded andmay be transmitted to each terminal, e.g., the terminals 181 and 182 inFIG. 1. Accordingly, the precoded data 220 may include controlinformation or data that is individually determined for each terminal.The precoded data 220 may include a power amplifier training field 230,a second channel estimation field 240, an individual control field 250,and a data field 260.

A terminal, e.g., the terminals 181 and 182, may detect a received frameusing the signal detection field 211, and may set a gain value of apower amplifier. The terminal may also estimate a coarse timesynchronization with respect to the received frame, and estimate afrequency offset.

The terminal may estimate a fine frequency offset using the firstchannel estimation field 212. The terminal may estimate a channel fordecoding of a channel estimation field.

The terminal may detect common control information with respect to adata frame currently being transmitted using the common control field213. The common control information may include one or more of: aprecoding method applied to the data frame, a number of terminalssupported by the data frame, a number of data frames included in thedata frame, a duration or a length of the second channel estimationfield 240, and a format of the second channel estimation field 240.

The power amplifier training field 230 may include a training signal toenhance a multi-antenna automatic gain control (AGC) performance. Theterminal may set a fine gain value of a power amplifier appropriate fora precoded signal using the power amplifier training field 230.

The terminal may accurately estimate a channel for decoding of theprecoded individual control field 250 and the data field 260 using thesecond channel estimation field 240.

The terminal may receive the individual control field 250 to detectindividual control information of a data frame transmitted to eachterminal. Control information corresponding to each terminal may beprecoded and simultaneously be transmitted.

Individual control information may include one or more of: a length ofthe data field 260 or the data frame transmitted to a correspondingterminal, a modulation and coding method applied to the data field 260,a channel bandwidth, a channel smoothing, a channel aggregation, anerror correction code, a length of a guard interval.

As described above, the information in the common control field 213 isnot precoded while the information in the individual control field 250is precoded. In other words, the information in the common control field213 may be decoded by each terminal in the system, but the informationincluded in the individual control field 250 may be decoded only by anintended terminal. As such, the type of information to be not precoded(and therefore to be decoded by each terminal) may be included in thecommon control field 213, and the type of information to be precoded(and therefore to be decoded only by an intended terminal) may beincluded in the individual control field 250. For example, a number ofdata frames included in the data frame, a duration or a length of thesecond channel estimation field 240 and a format of the second channelestimation field 240 described above as the information included in thecommon control field 213 may instead be included in the individualcontrol field 250. Also, a length of the data field 260 or the dataframe transmitted to a corresponding terminal, a modulation and codingmethod applied to the data field 260, a channel bandwidth, a channelsmoothing, a channel aggregation, an error correction code and a lengthof a guard interval described above as the information included in theindividual control field 250 may instead be included in the commoncontrol field 213.

FIG. 3 illustrates a structure of a data frame further including legacycontrol information to support terminals according to an embodiment.

Referring to FIG. 3, the data frame includes a signal detection field311, a first channel estimation field 312, a legacy control field 320, acommon control field 313, and precoded data 370.

Precoding is not applied to the signal detection field 311, the channelestimation field 312, and the common control field 313. In other words,it is not necessary to precode the signal detection field 311, thechannel estimation field 312, and the common control field 313.Accordingly, as similar to the description made above with reference toFIG. 2, a terminal, e.g., terminals 181 and 182 in FIG. 1, supporting aspace division multi-user multiple input multiple output (SD-MIMO)communication method may receive the signal detection field 311, thefirst channel estimation field 312, and the common control field 313 anduse these fields to receive the precoded data 370.

Precoding is not applied to the legacy control field 320. In otherwords, it is not necessary to precode the legacy control field 320.Accordingly, an existing terminal not supporting the SD-MIMOcommunication method may also receive the legacy control field 320 usingthe signal detection field 311, the first channel estimation field 312,and the common control field 313. Using the legacy control field 320,the existing terminal may detect information associated with amodulation and coding method applied to a data field 360 and a framelength.

The existing terminal may verify a time interval in which the precodeddata field 360 is transmitted and not receive the precoded data field360.

The terminal supporting the SD-MIMO communication method may receive theprecoded data field 360 using the common control field 313. The commoncontrol field 313 is similar to the common control field 213 of FIG. 2.

The precoded data 370 may include a power amplifier training field 330,a second channel estimation field 340, an individual control field 350,and the data field 360. The power amplifier training field 330, theindividual control field 350, and the data field 360 of FIG. 3 aresimilar to the power amplifier training field 230, the individualcontrol field 250, and the data field 260 of FIG. 2.

A terminal may estimate a channel between a transmission apparatus andthe terminal using the second channel estimation field 340. The secondchannel estimation field 340 may include a plurality of channelestimation signal groups 341 and 342. The terminal may estimate thechannel between the transmission apparatus and the terminal by combiningthe plurality of channel estimation signal groups 341 and 342.

When using the data frame of FIG. 3, an advanced terminal supporting theSD-MIMO communication method may receive the common control field 313and even an existing terminal not supporting the SD-MIMO communicationmethod may receive the legacy control field 320. The existing terminalmay detect a length of the precoded data field 360 transmitted to theadvanced terminal using the legacy control field 320 and then mayterminate a reception.

FIG. 4 illustrates a data frame when a particular terminal receives aplurality of data streams 491, 492, and 493 according to an embodiment.

Referring to FIG. 4, the data frame supports two terminals, for example,a first terminal and a second terminal, e.g., terminals 181 and 182 inFIG. 1. The data frame includes the plurality of data streams 491, 492,and 493. Among the data streams 491, 492, and 493, the data streams 491and 492 may be transmitted to the first terminal, and the data stream493 may be transmitted to the second terminal.

A signal detection field 411, a first channel estimation field 412, anda common control field 413 are not precoded and may be transmitted toeach of the first terminal and the second terminal. The signal detectionfield 411, the first channel estimation field 412, and the commoncontrol field 413 of FIG. 4 include similar information to the signaldetection field 211, the first channel estimation field 212, and thecommon control field 213 of FIG. 2.

Precoded data 420 is precoded with respect to the particular terminaland may be decoded only by the particular terminal to which it isdirected. In one example, only the particular terminal would have thecapability of decoding the precoded data 420. The precoded data 420included in each of the data streams 491, 492, and 493 may include apower amplifier training field 430, a second channel estimation field440, an individual control field 450, and a data field 460.

The first terminal may decode precoded data 431, 441, 442, 451, and 461included in the data stream 491. The first terminal may also decodeprecoded data 432, 443, 444, and 462 included in the data frame 492. Thesecond terminal may decode precoded data 433, 445, 452, and 463 includedin the data stream 493.

The power amplifier training field 430 is precoded and transmitted toeach of the first terminal and the second terminal. The power amplifiertraining field 430 of FIG. 4 is similar to the power amplifier trainingfield 230 of FIG. 2.

The second channel estimation field 440 included in each of the datastreams 491, 492, and 493 may include at least one of channel estimationsignal groups 441, 442, 443, 444, and 445.

A number of channel estimation signal groups included in each of thedata streams 491, 492, and 493 may be determined based on a number ofdata streams to be transmitted to each of the first terminal and thesecond terminal. In other words, there may be one channel estimationgroup for each respective data stream to be transmitted.

For example, when two data streams 491 and 492 are transmitted to thefirst terminal, the data stream 491 may include at least two channelestimation signal groups, e.g., the channel estimation signal groups 441and 442; and the data stream 492 may include at least two channelestimation signal groups, e.g., the channel estimation group 443 and444.

When only the single data stream 493 is transmitted to the secondterminal, the data stream 493 may include a single channel estimationsignal group, e.g., the channel estimation signal group 445.

The first terminal receiving the data streams 491 and 492 may estimate achannel between a plurality of transmit antennas and the first terminalby combining the channel estimation signal groups 441, 442, 443, and444. In other words, all of the channel estimation groups in eachreceived stream, e.g., data streams 491 and 492 in the illustratedexample, may be used to estimate the channel.

The second terminal receiving the single data stream 493 may estimate achannel between a transmit antenna and the second terminal using onlythe channel estimation signal group 445. Again, all of the channelestimation groups in each received stream, e.g., data stream 493 byitself, in the illustrated example, may be used to estimate the channel.

Individual control information included in each of individual controlfields 451 and 452 includes information similar to the individualcontrol information included in the individual control field 250 of FIG.2.

Each of the first terminal and the second terminal may be aware of anumber of data streams transmitted to a corresponding terminal based onthe individual control information. The individual control informationmay keep track of how many data streams are transmitted. Each of thefirst terminal and the second terminal may be aware of the number ofchannel estimation signal groups included in each data stream based onthe number of data streams transmitted to each of the first terminal andthe second terminal. The individual control information may keep trackof how many channel estimation signal groups are included.

Each of the first terminal and the second terminal may estimate achannel using a corresponding channel estimation signal group. The firstand second terminals may also decode data fields 461, 462, and 463transmitted to each of the first terminal and the second terminal.

In FIG. 4, two terminals, e.g., terminals 181 and 182, may receive dataframes. According to another embodiment, a single terminal or at leastthree terminals may receive data frames. In one example, a number ofchannel estimation signal groups included in the second channelestimation field 440 may be determined based on a number of data streamsreceived by each terminal.

FIG. 5 illustrates an example of a data frame in which data streams areindependently separated and transmitted using precoding.

Referring to FIG. 5, the data frame may include three data streams 591,592, and 593 in order to support two terminals, for example, a firstterminal and a second terminal. The data streams 591 and 592 may betransmitted to the first terminal, and the data stream 593 may betransmitted to the second terminal.

A second channel estimation field 540 included in each of the datastreams 591, 592, and 593 may include channel estimation signal groups541, 542, and 543 in the same time interval. When the data streams 591,592, and 593 are independently separated and transmitted, each of thefirst terminal and the second terminal may estimate a channel between abase station and each of the first terminal and the second terminalbased on the simultaneously transmitted channel estimation signal groups541, 542, and 543.

A signal detection field 511, a first channel estimation field 512, acommon control field 513, a power amplifier training field 530, anindividual control field 550, and a data field 560 of FIG. 5 areconfigured to be similar to the description made above for similar itemswith reference to FIGS. 2 through 4.

In FIG. 5 two terminals receiving data frames were described. Accordingto another embodiment, a single terminal or at least three terminals mayreceive data frames. In one example, the channel estimation signalgroups 541, 542, and 543 included in the second channel estimation field540 may be included in the same time interval.

FIG. 6 illustrates an example of data streams including channelestimation signal groups in different time intervals with respect to thesame terminal according to an embodiment.

Referring to FIG. 6, data streams 691 and 692 are transmitted to a firstterminal, and data streams 693, 694, and 695 are transmitted to a secondterminal.

Each of the data streams 691, 692, 693, 694, and 695 includes a secondchannel estimation field 640 to accurately estimate a channel between atransmission apparatus and each of the first terminal and the secondterminal. The second channel estimation field 640 may include channelestimation signal groups 641, 642, 643, 644, and 645.

The data streams 691 and 692 include the channel estimation signalgroups 641 and 642 in different time intervals, respectively. In thedifferent data streams 691 and 692 transmitted to the first terminal, atime interval of the channel estimation signal group 641 does notoverlap a time interval of the channel estimation group 642.

Similarly, in the different data streams 693, 694, and 695 transmittedto the second terminal, time intervals of the channel estimation signalgroups 643, 644, and 645 do not overlap each other.

The first terminal may estimate a channel between a transmit antenna anda receive antenna using the channel estimation signal groups 641 and642. The second terminal may also estimate a channel between a transmitantenna and a receive antenna using the channel estimation signal groups643, 644, and 645.

A signal detection field 611, a first channel estimation field 612, acommon control field 613, a power amplifier training field 630, anindividual control field 650, and a data field 660 of FIG. 6 areconfigured to be similar to the description made above for similar itemswith reference to FIGS. 2 through 5.

In FIG. 6 two terminals receiving data frames were described. Accordingto another embodiment, a single terminal or at least three terminals mayreceive data frames. In one example, channel estimation signal groupsincluded in different data streams received by the same terminal may beincluded in different time intervals, respectively.

FIG. 7 illustrates an example of data streams including channelestimation signal groups in different time intervals with respect todifferent terminals according to an embodiment.

Referring to FIG. 7, data streams 791 and 792 are transmitted to a firstterminal, and data streams 793 and 794 are transmitted to a secondterminal.

Data streams transmitted to different terminals may include channelestimation signal groups in different time intervals. For example, afirst set of channel estimation signal groups 741, 742, 743, and 744that are included in the data streams 791 and 792 transmitted to thefirst terminal, and a second set of channel estimation signal groups745, 746, 747, and 748 that are included in the data streams 793 and 794transmitted to the second terminal may be included in different timeintervals. Accordingly, it is possible to completely remove aninterference effect and accurately estimate a channel with respect todifferent terminals.

Precoded data transmitted to the same terminal may include channelestimation signal groups in the same time interval. In FIG. 7, the firstterminal may estimate a channel between a transmit antenna and a receiveantenna by combining the first set of channel estimation signal groups741, 742, 743, and 744. The second terminal may estimate a channelbetween a transmit antenna and a receive antenna by combining the secondset of channel estimation signal groups 745, 746, 747, and 748.

A signal detection field 711, a first channel estimation field 712, acommon control field 713, a power amplifier training field 730, anindividual control field 750, and a data field 760 of FIG. 7 areconfigured to be similar to the description made above for similar itemswith reference to FIG. 2.

In FIG. 7 two terminals receiving data frames were described. Accordingto another embodiment, a single terminal or at least three terminals mayreceive data frames. In one example, data streams transmitted todifferent terminals may include channel estimation signal groups indifferent time intervals.

FIG. 8 illustrates an example of a data frame in which data stream areindependently separated and transmitted using precoding.

Referring to FIG. 8, data streams 891 and 892 may be transmitted to afirst terminal, and data streams 893 and 894 may be transmitted to asecond terminal.

Each of the data streams 891, 892, 893, and 894 may include a secondchannel estimation field 840 to estimate a channel between atransmission apparatus and each of the first terminal and the secondterminal. The second channel estimation field 840 may include channelestimation signal groups 841, 842, 843, 844, 851, 852, 853, 854, 855,856, 857, and 858.

The channel estimation signal groups 841, 842, 843, and 844 included inthe data streams 891 and 892 transmitted to the first terminal, and thechannel estimation signal groups 851, 852, 853, 854, 855, 856, 857, and858 included in the data streams 893 and 894 transmitted to the secondterminal may temporally overlap.

The first terminal may apply an orthogonality to the channel estimationsignal groups 841, 842, 843, and 844 by multiplying a unitary matrix andeach of the channel estimation signal groups 841, 842, 843, and 844. Thesecond terminal may apply the orthogonality to the channel estimationsignal groups 851, 852, 853, 854, 855, 856, 857, and 858 by multiplyinga unitary matrix and each of the channel estimation signal groups 851,852, 853, 854, 855, 856, 857, and 858. Undesirable signals can then bediscarded due to the applied orthogonality. Each of the first terminaland the second terminal may estimate a channel between a transmissionapparatus and each of the first terminal and the second terminal usingthe channel estimation signal groups 841, 842, 843, 844, 851, 852, 853,854, 855, 856, 857, and 858 with the assigned orthogonality.

A signal detection field 811, a first channel estimation field 812, acommon control field 813, a power amplifier training field 830, anindividual control field 860, and a data field 870 of FIG. 7 areconfigured to be similar to the description made above for similar itemswith reference to FIG. 2.

In FIG. 8 two terminals receiving data frames were described. Accordingto another embodiment, a single terminal or at least three terminals mayreceive data frames. In one example, channel estimation signal groupsincluded in data streams may temporally overlap. Each of the terminalsmay estimate a channel using a unitary matrix.

FIG. 9 illustrates a configuration of a transmission apparatus 900according to an embodiment.

The transmission apparatus 900 may include a detection signal generator911, a first channel estimation signal generator 912, a common controlinformation generator 913, a power amplifier training signal generator920, an individual control information generator 930, a second channelestimation signal generator 940, a controller 950, a precoder 960, and atransmitter 970.

The detection signal generator 911 may generate a detection signal. Eachof terminals 980 and 990 may detect a data frame transmitted from thetransmission apparatus 900, using the detection signal included in thedata frame. Each of the terminals 980 and 990 may perform a timesynchronization with respect to a current data frame. In addition, eachof the terminals 980 and 990 may estimate a coarse frequency offsetusing the detection signal.

The first channel estimation signal generator 912 may generate a firstchannel estimation signal. Each of the terminals 980 and 990 mayestimate a fine frequency offset based on the first channel estimationsignal. In addition, each of the terminals 980 and 990 may receivenon-precoded common control information.

The detection signal and the first channel estimation signal are notprecoded and are transmitted to each of the terminals 980 and 990.

The common control information generator 913 may generate common controlinformation with respect to the terminals 980 and 990. Each of theterminals 980 and 990 may include at least one receive antenna. Forexample, the terminal 980 may include receive antennas 981 and 982, andthe terminal 990 may include a receive antenna 991.

The “common control information” denotes control information transmittedto all the terminals 980 and 990 included within a coverage of thetransmission apparatus 900. The common control information istransmitted without being precoded. The common control information mayinclude information associated with common controls of the data frame.The common control information may include a precoding method applied tothe data frame, a number of terminals supported by the data frame, andchannel estimation signal groups. The common control information is notprecoded with respect to a particular terminal and transmitted to allterminals receiving the data frame.

As described before, a number of data frames included in the data frame,a duration or a length of the second channel estimation field and aformat of the second channel estimation field may instead be included inthe individual control information to be describe below.

The power amplifier training signal generator 920 may generate a poweramplifier training signal. Each of the terminals 980 and 990 may performa multi-antenna AGC using the power amplifier training signal. Theprecoder 960 may generate the precoded data by additionally precodingthe power amplifier training signal.

The individual control information generator 930 may generate individualcontrol information with respect to each of the terminals 980 and 990.The “individual control information” denotes control informationindividually determined for each of the terminals 980 and 990. Theindividual control information may include one or more of: a data fieldor a data frame transmitted to a corresponding terminal, a modulationand coding method applied to the data field, a bandwidth of a usingchannel, a channel smoothing, a channel aggregation, an error correctioncode, a guard interval, and a precoding method applied to the dataframe.

As described before, a length of the data field or the data frametransmitted to a corresponding terminal, a modulation and coding methodapplied to the data field, a channel bandwidth, a channel smoothing, achannel aggregation, an error correction code and a length of a guardinterval may instead be included in the common control information.

The second channel estimation signal generator 940 may generate a secondchannel estimation signal used to estimate a channel for each ofmulti-accessing terminals 980 and 990. The second channel estimationsignal may include at least one channel estimation signal group.

The terminals 980 and 990 may receive a different number of datastreams. Each of the data streams may include a channel estimationsignal. A number of channel estimation signal groups included in eachchannel estimation signal may be determined based on a number of datastreams received by each of the terminals 980 and 990.

The controller 950 may individually determine a number of data streamstransmitted to each of the terminals 980 and 990. The controller 950 maydetermine a number of training signal groups included in each of thedata streams based on the number of data streams. The data frame mayinclude a plurality of data streams. The channel estimation signal mayinclude a plurality of channel estimation signal groups. The transmitter970 may transmit a plurality of precoded data to a particular terminalincluded in the plurality of terminals, e.g., either of the terminals980 and 990. Each of channel estimation signals included in theplurality of precoded data may be included in a different time interval.

The terminal 980 may receive a plurality of data streams. The datastreams received by the terminal 980 may include training signal groupsin different time intervals, respectively. When the training signalgroups do not overlap each other, the terminal 980 may effectivelyestimate a channel.

An example in which each of the terminals 980 and 990 estimates achannel between the transmission apparatus 900 and each of the terminals980 and 990 using the channel estimation signal group is described abovefor similar items with reference to FIGS. 4 through 8.

The precoder 960 may generate precoded data with respect to each of theterminals 980 and 990 by precoding the individual control informationand data with respect to each of the terminals 980 and 990. The precodeddata may be transmitted to each of the terminals 980 and 990. However,each of the terminals 980 and 990 may decode only precoded data that isprecoded with respect to a corresponding terminal.

The precoder 960 may generate the precoded data by additionallyprecoding the power amplifier training signal and the second channelestimation signal.

The transmitter 970 may transmit, to the terminals 980 and 990, a dataframe including a plurality of data streams. The transmitter 970 maytransmit, to the terminals 980 and 990, a data frame including thecommon control information and the precoded data according to amulti-user multiple input multiple output (MU-MIMO) communicationmethod. The transmitter 970 may transmit the data frame to each of theterminals 980 and 990 using a plurality of transmit antennas 971, 972,and 973. Each data stream may include a detection signal, a firstchannel estimation signal, and common control information that are notprecoded, and precoded data that is precoded with respect to each of theterminals 980 and 990.

Each of the terminals 980 and 990 may decode the non-precoded commoncontrol information and may also decode the precoded data precoded withrespect to a corresponding terminal.

Data included in the precoded data may be modulated by selecting asingle modulation method from various modulation methods based on achannel status. For example, the individual control information may bemodulated using a predetermined modulation method. The data may also beerror correction coded by selecting a single error correction codemethod from various error correction code methods. For example, theindividual control information may be error correction coded using apredetermined error correction code method. The modulation method andthe error correction code method applied to the data may be included inthe individual control information.

The individual control information may be modulated using a modulationmethod predetermined between the transmission apparatus 900 and each ofthe terminals 980 and 990, or may be error correction coded using anerror correction code method predetermined between the transmissionapparatus 900 and each of the terminals 980 and 990. For example, theterminals 980 and 990 may simply decode the individual controlinformation without reference to other control information, and maydecode data using the decoded individual control information.

The modulation method or the error correction code method applied to theindividual control information may be included in the common controlinformation.

FIG. 10 illustrates a configuration of a terminal according to anembodiment.

The terminal 1000 may include a receiver 1060, a signal detector 1011, afirst channel estimator 1012, a common control information decoder 1013,a power amplifier controller 1020, a second channel estimator 1030, adata decoder 1040, and an individual control information decoder 1050.

The receiver 1060 may receive a data frame from a transmission apparatus1070. The data frame may include a data stream or a plurality of datastreams. The data stream may include a signal detection field, a firstchannel estimation field, a common control field, and precoded data. Thetransmission apparatus 1070 may transmit the precoded data using aplurality of transmit antennas 1071, 1072, and 1073.

The signal detector 1011 may detect a signal transmitted from thetransmission apparatus 1070. The signal may be detected using adetection signal included in the signal detection field. The signaldetector 1011 may perform a coarse AGC using the detection signal, andmay also estimate a coarse frequency offset. The signal detector 1011may perform a time synchronization with respect to a current data frameusing the detection signal.

The first channel estimator 1012 may estimate a fine frequency offsetusing a first channel estimation signal included in the first channelestimation field. The first channel estimator 1012 may estimate achannel between the transmission apparatus 1070 and the terminal 1000 inorder to decode common control information.

The common control information decoder 1013 may decode the commoncontrol information from the data frame.

The “common control information” denotes control information decodableby the terminal 1000 and by a terminal 1080 included within a coverageof the transmission apparatus 1070. The common control information mayinclude the data frame transmitted to the terminals 1000 and 1080. Thecommon control information may include one or more of: a precodingmethod applied to the data frame, a number of terminals supported by thedata frame, a number of data streams included in the data frame, and aninterval or a length of a second channel estimation field, and a formatof the second channel estimation field. As described before, a number ofdata frames included in the data frame, a duration or a length of thesecond channel estimation field and a format of the second channelestimation field may instead be included in the individual controlinformation. The common control information is transmitted without beingprecoded with respect to a particular terminal.

The power amplifier controller 1020 may accurately control a gain of apower amplifier using the power amplifier training signal included inthe power amplifier training field.

The second channel estimator 1030 may estimate a channel between thetransmission apparatus 1070 and the terminal 1000 using the secondchannel estimation signal included in the second channel estimationfield. The second channel estimation signal may include at least onechannel estimation signal group.

The terminal 1000 may receive a plurality of data streams. According toan example embodiment, a number of channel estimation signal groupsincluded in each of the data streams received by the terminal 1000 maybe determined based on a number of the data streams received by theterminal 1000.

According to another example embodiment, channel estimation signalsincluded in the data streams received by the first terminal 1000 may beincluded in different time intervals.

An example in which the terminal 1000 estimates a channel between theterminal 1000 and the transmission apparatus 1070 using the channelestimation signal group is described above for similar items withreference to FIGS. 4 through 8.

The individual control information decoder 1050 may decode theindividual control information based on the common control informationand a channel estimation result of the second channel estimator 1030.The “individual control information” denotes control informationindividually determined with respect to each of the terminals 1000 and1080. The individual control information may include one or more of: alength of a data field or a data frame transmitted to a correspondingterminal, a modulation and coding method applied to the data field, achannel bandwidth, a channel smoothing, a channel aggregation, an errorcorrection code, a length of a guard interval, and a precoding methodapplied to the data frame. As described before, a length of the datafield or the data frame transmitted to a corresponding terminal, amodulation and coding method applied to the data field, a channelbandwidth, a channel smoothing, a channel aggregation, an errorcorrection code and a length of a guard interval may instead be includedin the common control information.

The data decoder 1040 may decode data included in a data stream, basedon the individual control information and a channel estimation result ofthe second channel estimator 1030. A modulation method selected fromvarious modulation methods or an error correction code method selectedfrom various error correction code methods may be applicable to the datatransmitted to each of the terminals 1000 and 1080, based on a channelstatus.

A modulation method or an error correction code method predeterminedbetween the terminal 100 and the transmission apparatus 1070 may beapplicable to the individual control information. In one example, theterminal 1000 may simply decode the individual control informationwithout reference to other control information, and may decode datausing the decoded individual control information.

The transmission apparatus 1070 may precode and transmit individualcontrol information and data determined with respect to each of theterminals 1000 and 1080.

FIG. 11 illustrates a method of receiving data according to anembodiment.

In operation 1110, a terminal may receive a data frame from atransmission apparatus. The terminal may detect the data frame using adetection signal included in the data frame. The terminal may perform acoarse AGC using the detection signal. The terminal may perform a timesynchronization with respect to the current data frame using thedetection signal.

In operation 1120, the terminal may perform a first channel estimationusing a first channel estimation signal included in the data frame. The“first channel estimation” denotes an operation of estimating a channelbetween the transmission apparatus and the terminal in order to decode anon-precoded field included in the data frame. Also, in operation 1120,the terminal may estimate a fine frequency offset using the firstchannel estimation signal.

In operation 1130, the terminal may decode common control informationincluded in the data frame. The terminal may decode precoded dataincluded in the data frame, based on the common control information.

In operation 1140, the terminal may perform a fine AGC using a poweramplifier training signal included in the data frame.

In operation 1150, the terminal may perform a second channel estimationusing the second channel estimation field included in the data frame.The “second channel estimation” denotes an operation of estimating achannel between the transmission apparatus and the terminal in order todecode precoded data.

In operation 1160, the terminal may decode the individual controlinformation included in the data frame.

In operation 1170, the terminal may decode data included in the dataframe, based on a second channel estimation result and the individualcontrol information.

FIG. 12 illustrates a method of transmitting data according to anembodiment.

In operation 1210, a transmission apparatus may generate a detectionsignal. A terminal may detect a data frame transmitted from thetransmission apparatus, using the detection signal included in the dataframe, and may perform a coarse frequency offset. The terminal mayperform a time synchronization with respect to the current data frameusing the detection signal.

In operation 1220, the transmission apparatus may generate a firstchannel estimation signal. The terminal may estimate a channel betweenthe transmission apparatus and the terminal based on the first channelestimation signal, and may decode non-precoded information ornon-precoded signals using the above estimation result.

In operation 1230, the transmission apparatus may generate commoncontrol information. The common control information may include controlinformation associated with the data frame transmitted from thetransmission apparatus.

In operation 1240, the transmission apparatus may generate a poweramplifier training signal. The terminal may perform a fine AGC using thepower amplifier training signal.

In operation 1250, the transmission apparatus may generate individualcontrol information. The “individual control information” denotescontrol information individually determined with respect to eachterminal.

In operation 1260, the transmission apparatus may generate a secondchannel estimation signal. The terminal may estimate a channel betweenthe transmission apparatus and the terminal using the second channelestimation signal, and may decode a precoded signal or precodedinformation using the above estimation result.

The second channel estimation signal may include a plurality of trainingsignal groups. A number of channel estimation signal groups included inthe second channel estimation signal may be determined based on a numberof data streams received by the terminal.

The channel estimation signal groups included in the second channelestimation signal may be included in different time intervals.

In operation 1270, the transmission apparatus may generate precoded databy precoding the data individual control information and data withrespect to each terminal. The transmission apparatus may generate theprecoded data by additionally precoding the power amplifier trainingsignal and the second channel estimation signal.

In operation 1280, the transmission apparatus may transmit, to aplurality of terminals, common control information and the precodeddata. The data frame may include the detection signal and the firstchannel estimation signal. The transmission apparatus may transmit thedata frame using a MU-MIMO communication method. In one example, thecommon control information may include information associated with anumber of terminals supported by the MU-MIMO communication method.

The processes, functions, methods and/or software described above may berecorded, stored, or fixed in one or more computer-readable storagemedia that includes program instructions to be implemented by a computerto cause a processor to execute or perform the program instructions. Themedia may also include, alone or in combination with the programinstructions, data files, data structures, and the like. The media andprogram instructions may be those specially designed and constructed, orthey may be of the kind well-known and available to those having skillin the computer software arts. Examples of computer-readable mediainclude magnetic media, such as hard disks, floppy disks, and magnetictape; optical media such as CD-ROM disks and DVDs; magneto-opticalmedia, such as optical disks; and hardware devices that are speciallyconfigured to store and perform program instructions, such as read-onlymemory (ROM), random access memory (RAM), flash memory, and the like.Examples of program instructions include machine code, such as producedby a compiler, and files including higher level code that may beexecuted by the computer using an interpreter. The described hardwaredevices may be configured to act as one or more software modules inorder to perform the operations and methods described above, or viceversa. In addition, a computer-readable storage medium may bedistributed among computer systems connected through a network andcomputer-readable codes or program instructions may be stored andexecuted in a decentralized manner.

As a non-exhaustive illustration only, the terminal device describedherein may refer to mobile devices such as a cellular phone, a personaldigital assistant (PDA), a digital camera, a portable game console, andan MP3 player, a portable/personal multimedia player (PMP), a handhelde-book, a portable laptop PC, a global positioning system (GPS)navigation, and devices such as a desktop PC, a high definitiontelevision (HDTV), an optical disc player, a setup and/or set-top box,and the like capable of wireless communication or network communicationconsistent with that disclosed herein.

A computing system or a computer may include a microprocessor that iselectrically connected with a bus, a user interface, and a memorycontroller. It may further include a flash memory device. The flashmemory device may store N-bit data via the memory controller. The N-bitdata is processed or will be processed by the microprocessor and N maybe 1 or an integer greater than 1. Where the computing system orcomputer is a mobile apparatus, a battery may be additionally providedto supply operation voltage of the computing system or computer.

It will be apparent to those of ordinary skill in the art that thecomputing system or computer may further include an application chipset,a camera image processor (CIS), a mobile Dynamic Random Access Memory(DRAM), and the like. The memory controller and the flash memory devicemay constitute a solid state drive/disk (SSD) that uses a non-volatilememory to store data.

A number of example embodiments have been described above. Nevertheless,it will be understood that various modifications may be made. Forexample, suitable results may be achieved if the described techniquesare performed in a different order and/or if components in a describedsystem, architecture, device, or circuit are combined in a differentmanner and/or replaced or supplemented by other components or theirequivalents. Accordingly, other implementations are within the scope ofthe following claims.

What is claimed is:
 1. A transmission apparatus to transmit data,comprising common control information, individual control information,and a data field, to terminals comprising at least one receive antenna,the transmission apparatus comprising: a common control informationgenerator configured to generate the common control information withrespect to the terminals; an individual control information generatorconfigured to generate the individual control information with respectto each of the terminals; a precoder configured to generate precodeddata with respect to each of the terminals by precoding the individualcontrol information and the data field with respect to each of theterminals; a transmitter configured to transmit, to the terminals, adata frame comprising the common control information and the precodeddata according to a multi-user multiple input multiple output (MU-MIMO)communication method, and a power amplifier training signal generatorconfigured to generate a power amplifier training signal for amulti-antenna automatic gain control (AGC) of each of the terminals,wherein the precoder is further configured to generate the precoded databy additionally precoding the power amplifier training signal.
 2. Thetransmission apparatus of claim 1, wherein the common controlinformation comprises one or more of: a precoding method applied to thedata frame, a number of terminals supported by the data frame, a numberof data streams included in the data frame, a duration or a length of achannel estimation field included in the data frame, and a format of thechannel estimation field.
 3. The transmission apparatus of claim 1,wherein the individual control information comprises one or more of: alength of the data frame, a modulation and coding method applied to thedata with respect to each of the terminals, a channel bandwidth, achannel smoothing, a channel aggregation, an error correction code, anda length of a guard interval.
 4. The transmission apparatus of claim 1,further comprising: a channel estimation signal generator configured togenerate a channel estimation signal used for a channel estimation ofeach of the terminals, wherein the precoder is further configured togenerate the precoded data by additionally precoding the channelestimation signal.
 5. The transmission apparatus of claim 4, furthercomprising: a controller configured to: individually determine a numberof data streams transmitted to each of the terminals; and determine anumber of channel estimation signal groups based on the number of datastreams, wherein the data frame comprises a plurality of data streams,and wherein the channel estimation signal comprises a plurality ofchannel estimation signal groups.
 6. The transmission apparatus of claim4, wherein: the transmitter is further configured to transmit aplurality of precoded data to a particular terminal included in theplurality of terminals; and each of channel estimation signals includedin the plurality of precoded data is included in a different timeinterval.
 7. The transmission apparatus of claim 1, wherein theindividual control information is modulated using a predeterminedmodulation method, or is error correction coded using a predeterminederror correction code method.
 8. A terminal wirelessly connected to atransmission apparatus, the terminal comprising: a receiver configuredto receive a data frame from the transmission apparatus; a commoncontrol information decoder configured to decode, from the data frame,common control information commonly transmitted to the terminal and toanother terminal wirelessly connected to the transmission apparatus; anindividual control information decoder configured to decode, from thedata frame, individual control information individually determined withrespect to the terminal using the common control information; and a datadecoder configured to decode data, included in the data frame, based onthe individual control information, wherein the individual controlinformation and the data are precoded.
 9. The terminal of claim 8,wherein the common control information comprises one or more of: aprecoding method applied to the data frame, a number of terminalssupported by the data frame, a number of data streams included in thedata frame, a duration or a length of a channel estimation fieldincluded in the data frame, and a format of the channel estimationfield.
 10. The terminal of claim 8, wherein the individual controlinformation comprises one or more of: a length of the data frame, amodulation and coding method applied to the data with respect to each ofthe terminals, a channel bandwidth, a channel smoothing, a channelaggregation, an error correction code, and a length of a guard interval.11. The terminal of claim 8, wherein the individual control informationdecoder is further configured to decode the individual controlinformation using a predetermined modulation method or a predeterminederror correction code method.
 12. The terminal of claim 8, furthercomprising: a channel estimator configured to estimate a channel betweenthe terminal and the transmission apparatus based on a channelestimation signal, wherein the data frame comprises the channelestimation signal, and wherein the data decoder is further configured todecode the data based on the estimated channel.
 13. The terminal ofclaim 12, wherein: the data frame comprises a plurality of data streams;each of the data streams comprises the channel estimation signal; andthe channel estimation signal included in each of the data streams isincluded in a different time interval.
 14. The terminal of claim 12,wherein: the data frame comprises a plurality of data streams; thechannel estimation signal comprises a plurality of channel estimationsignal groups; and a number of the channel estimation signal groups isdetermined based on a number of the data streams.
 15. The terminal ofclaim 8, wherein the receiver is further configured to receive the dataframe via at least one receive antenna.
 16. A method of transmittingdata, comprising common control information, individual controlinformation, and a data field, to terminals comprising at least onereceive antenna, the method comprising: generating the common controlinformation with respect to the terminals; generating the individualcontrol information with respect to each of the terminals; generatingprecoded data with respect to each of the terminals by precoding theindividual control information and the data field with respect to eachof the terminals; transmitting, to the plurality of terminals, a dataframe comprising the common control information and the precoded dataaccording to a multi-user multiple input multiple output (MU-MIMO)communication method; and generating a channel estimation signal usedfor a channel estimation of each of the terminals, wherein the precodingcomprises generating the precoded data by additionally precoding thechannel estimation signal.
 17. The method of claim 16, wherein thecommon control information comprises one or more of: a precoding methodapplied to the data frame, a number of terminals supported by the dataframe, a number of data streams included in the data frame, a durationor a length of a channel estimation field included in the data frame,and a format of the channel estimation field.
 18. The method of claim16, wherein the individual control information comprises one or more of:a length of the data frame, a modulation and coding method applied tothe data with respect to each of the terminals, a channel bandwidth, achannel smoothing, a channel aggregation, an error correction code, anda length of a guard interval.
 19. A method of receiving data, the methodcomprising: receiving a data frame from a transmission apparatus;decoding, from the data frame, common control information commonlytransmitted to terminals wirelessly connected to the transmissionapparatus; decoding, from the data frame, individual control informationindividually determined with respect to one of the terminals using thecommon control information; and decoding data, included in the dataframe, based on the individual control information, wherein theindividual control information and the data are precoded.
 20. The methodof claim 19, further comprising: estimating a channel between one of theterminals and the transmission apparatus based on a channel estimationsignal, wherein the data frame comprises the channel estimation signal,and the decoding of the data comprises decoding the data based on theestimated channel.
 21. The method of claim 19, wherein: the data framecomprises a plurality of data streams; each of the data streamscomprises a channel estimation signal; and the channel estimation signalincluded in each of the data streams is included in a different timeinterval.
 22. A non-transitory computer-readable recording mediumstoring a program to implement the method of claim
 16. 23. Thetransmission apparatus of claim 1, further comprising: a channelestimation signal generator configured to generate a channel estimationsignal used for a channel estimation of each of the terminals.
 24. Thetransmission apparatus of claim 1, wherein the common controlinformation comprises information that is required for decoding one or acombination of the data field and the individual control information.25. The transmission apparatus of claim 1, wherein the data fieldcomprises an audible message signal.